1. Field of the Invention
This invention relates generally to a vortex generation device for reducing drag on an upswept aircraft fuselage afterbody.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Many cargo aircraft are designed with relatively short landing gear to provide low ground clearance to facilitate direct cargo onload and offload without the use of scissors trucks and other cargo lift devices. Such aircraft are also often designed to include an upswept aft fuselage section that positions an empennage of the aircraft clear of the ground when the aircraft are rotated for takeoff and when the aircraft are landing at slow speed and high angle of attack on approaches to short landing fields. An aft wall of the upswept aft fuselage section of such aircraft typically includes a large main cargo door that opens downward about a horizontal axis adjacent a cargo floor of the aircraft to form a ramp that may be used to onload and offload of cargo and personnel when the aircraft is on the ground. The main cargo door may also be opened in flight to offload cargo via paradrop or low altitude extraction.
The upswept aft fuselage wall typically contributes significant drag to the aircraft because vortices are formed when air sweeping laterally inward around the corners of the upswept aft fuselage meets air flowing aft and upward from underneath the fuselage. These vortices tend to cause flow separation to occur earlier than it otherwise would, imparting significant profile drag. Since profile drag tends to rise with the square of airspeed its effects become more pronounced at higher airspeeds. Those effects include increased fuel consumption rates and decreases in range, endurance, and airspeed.
Fin-like projections mounted on the mold line of an aircraft fuselage are known to generate vortices. However, when such projections are included aft of an aft side parachute jump door of an aircraft, they can snag parachute drop lines of paratroopers or parachuted cargo.